1. Field of the Invention
The present invention relates to a solid-state image-capturing apparatus that converts an analog signal representing an image of a subject that is formed on a surface of an image-capturing device into a digital signal and performs image processing on the digital signal, thereby obtaining a desirable image similar to a scene perceived by human eyes, a camera including the solid-state image-capturing apparatus, and a signal processing method.
2. Description of the Related Art
In the field of image-capturing apparatuses, such as a digital still camera (DSC) or a camera included in a mobile phone, that outputs a digital video signal, with demands for smaller DSCs and smaller mobile phones, a thinner and smaller optical element (e.g., lens) and an optical system including fewer elements have been required in recent years. However, it is difficult to image a subject on a surface of an image-capturing device with high accuracy by using such lenses satisfying those demands, which causes many problems.
One of the problems is that light level is low at a periphery of the image-capturing device compared with near the center region thereof, which makes it difficult to control contrast at the periphery rather than at the center. To solve the problem, for example, shading correction is performed on a video signal that is converted into a digital signal, i.e., a digital video signal. Specifically, electrical shading correction is performed using correction coefficient according to a position of the surface of the image-capturing device (see, for example, Japanese Patent Application Laid-open No. 2001-339736).
There is also the solid-state image-capturing apparatus that is capable of changing an image-capturing condition, for example, an analog gain, that is used for the image-capturing device. With this solid-state image-capturing apparatus, because an image signal that is output from the image-capturing device varies according to the image-capturing condition, an optimum operation condition for various kinds of image processing to be processed downstream of the image-capturing device varies according to the image-capturing condition. However, with the technique described in the Japanese Patent Application Laid-open No. 2001-339736, the correction coefficient is determined only in terms of the position on the surface of the image-capturing device. Accordingly, an optimum processing in response to the image-capturing condition is not implemented.